[SideburnsOfDoom]

Yes, that was a mistake. Diesel was promoted as lower C02 than petrol engines, before the problems with particulates were well known. (1)

This is of course changing now. (2)

As noted in the second link, a factor is the "Volkswagen emissions scandal", AKA "Dieselgate" (3)

1) https://www.bbc.co.uk/news/uk-politics-41985715

2) https://www.autoexpress.co.uk/car-news/consumer-news/98747/d...

3) https://en.wikipedia.org/wiki/Volkswagen_emissions_scandal